Pipelines are employed in varied environments to carry many different types of media. For instance, pipelines can be located in both topside and subsea environments and may carry media ranging from portable water to petroleum-based gases and liquids. The pipes used in the pipeline are typically made of carbon steel, stainless steel, or a duplex, and can have diameters on the order of ½ inch to greater than 42 inches. Furthermore, pressures within the pipeline can approach and exceed approximately 9000 psi.
One particularly harsh application involves subsea pipelines. These pipelines are subjected to extreme environmental and operational conditions and, in some situations, are lined or clad with a corrosion resistant alloy (“CRA”) to inhibit degradation of the main carrier pipe by gases, including hydrogen sulfide. Problems occur when a subsea CRA clad/lined pipeline develops a leak. Practicality often dictates that the pipeline be repaired in the subsea environment, which may require use of a costly and complex hyperbaric welding process. Depending on the subsea depth of the pipeline, repair by a human diver may not be possible, which may require some type of robotic tool to repair the leaking pipeline.
MORGRIP connectors, manufactured by Hydratight Limited, have proven to be a viable solution to repairing leaks in non-CRA clad/lined subsea pipelines. When a leak in the pipeline is detected, the damaged section is cut and removed from the pipeline. The appropriate MORGRIP connectors are then installed onto the cut ends of the pipe. Finally, a splice or spool piece is positioned between and secured to the MORGRIP connectors to reestablish a leak-free pipeline.
Typical mechanical connectors, however, do not fully inhibit media flowing within the pipeline from coming into contact with the bare end faces of the cut pipes. Therefore, potentially damaging media may interact with the bare ends and degrade the pipe, ultimately reducing the integrity of any repair and associated mechanical connector. A mechanical connector used to repair a subsea CRA clad/lined pipeline should inhibit the media within the pipe from interacting with the unprotected ends of the cut pipe and, in CRA lined applications, further being interspersed between the inner wall of the carrier pipe and the outer wall of the CRA lining. This requirement is further complicated by tolerances of the inner diameter, outer diameter, and wall thickness of the pipe, irregularities in the roundness of the pipe, and additional imperfections related to the orientation of the cut end face relative to the axis of the pipe. Moreover, thermal dynamics factors must be accounted for because thermal expansion and contraction coefficients of each component can impact the operational characteristics and performance of the overall connector. From a business standpoint, a mechanical connector should not excessively reduce the media flow through the repaired pipeline, require minimal costly pipe preparation, and avoid further damaging the pipeline during the repair.
In light of at least the above design considerations and the challenges presented by them, a need exists for an improved pipe end connector that reduces the potential for degradation of cut pipe ends.